This invention relates to a catalyst composition useful in the removal of sulfur and nitrogen from gas oils, as practiced in the hydrocarbon refining industry, in a process commonly referred to as hydroprocessing.
A solid catalyst, such as the material of concern of the present invention, is contained inside of a reactor in which the material to be hydroprocessed is passed over the catalyst together with a flow of hydrogen, at comparatively moderate temperatures and pressures and flow rates. In customary practice, the catalyst consists of metal oxides on a support, the oxides being converted to sulfides to produce an active, stable catalyst prior to use. The product is a gas oil in which the sulfur and nitrogen content has been substantially reduced. Any improvement in this process, especially as relating to the use of a material having improved activity for catalyzing this reaction, will result in significant economic savings.
Catalytic hydroprocessing, as currently practiced, uses a material consisting of active metals, either molybdenum or tungsten and either nickel or cobalt, possibly with promoters, on an inert support consisting of alumina or silica or mixtures of these. The use of different supports or other supported metals has been found to either enhance or decrease the activity of the base catalyst. Also, varying the method of preparation of these materials can also result in a change in catalytic activity.
Hydroprocessing catalysts have been traditionally prepared by depositing aqueous solutions of molybdenum, tungsten, nickel and cobalt salts onto a support; either in separate steps or by co-deposition. Alternately, the support and the deposited metals can be formed simultaneously. Intermediate and final calcining steps are necessary to produce the final form of the catalyst, an alumina support holding more-or-less dispersed molybdenum, tungsten, nickel and cobalt oxides. Numerous variations in both methods and compositions of this procedure have been described.
Improvements in these materials can be effected. One such method through the addition of other elements, specifically those designed to interact with the support or catalytically active metals. By doing so the utilization of active metals can be increased without necessarily adversely affecting support properties and without the need for increasing the content of active metals. Hence a small increase in the cost of the catalyst, as necessitated by the additional components, can result in significant savings by permitting operation of the hydroprocessing process at less severe conditions or at higher throughput.
Therefore, it is an object of the present invention to a material, suitable for use as a hydroprocessing catalyst, containing molybdenum, tungsten, nickel and cobalt on a support, and containing a third metal.
Another object of the present invention to provide a material in which the third metal is an metal alkoxide deposited in an essentially water-free environment, while the other metals are deposited in aqueous solutions.
A further object of the present invention to provide a material in which the third metal is selected from a group consisting of vanadium, niobium, or tantalum, or combinations of these three.
Moreover, another object of the present invention to provide a process for the removal of sulfur and nitrogen from hydrocarbon streams, employing a material of this disclosure as an improved hydroprocessing catalyst.